Lead-free and halogen-free solder paste

Abstract

The present application relates to the technical field of welding materials, and particularly to a lead-free and halogen-free solder paste, including a solder alloy powder and a welding flux with a mass ratio of 85-90:10-15, the solder alloy powder is Sn-2.5Be-0.8Ag-0.5Cu alloy powder, and the welding flux includes the following components: itaconic acid, succinic acid, a surfactant, a thixotropic agent, modified rosin, a composite solvent, a corrosion inhibitor, and an acrylic type activator. Its preparation method includes the following steps: mixing the modified rosin, the composite solvent and the corrosion inhibitor, heating under stirring, cooling, adding itaconic acid, succinic acid and the acrylic type activator under stirring, cooling, adding the thixotropic agent for emulsification dispersion, adding the surfactant under stirring, grinding to obtain a welding flux after cooling, and stirring the solder alloy powder and the welding flux under vacuum to obtain the solder paste.

What is claimed is: 
     
       1. A lead-free and halogen-free solder paste comprising a solder alloy powder and a welding flux, wherein a mass ratio of the solder alloy powder to the welding flux is (85-90):(10-15), the solder alloy powder is Sn-2.5Be-0.8Ag-0.5Cu alloy powder, and the welding flux comprises the following components in parts by weight:
 1-3 parts of itaconic acid, 
 3-5 parts of succinic acid, 
 1-3 parts of a surfactant, 
 3-8 parts of a thixotropic agent, 
 10-20 parts of modified rosin, 
 20-40 parts of a composite solvent, 
 3-8 parts of a corrosion inhibitor, and 
 5-10 parts of an acrylic activator; 
 wherein the acrylic activator is obtained after allyl glycidyl ether and bisphenol A diglycidyl ether are reacted with acrylic acid, acrylic anhydride, and cyclohexylamine. 
 
     
     
       2. The lead-free and halogen-free solder paste according to  claim 1 , wherein the acrylic activator is prepared by the following raw materials in parts by weight:
 20-30 parts of the allyl glycidyl ether, 5-10 parts of the bisphenol A diglycidyl ether, 15-20 parts of the acrylic acid, 5-10 parts of the acrylic anhydride, 15-20 parts of the cyclohexylamine, 1-3 parts of benzyl 1H-imidazole-1-carbodithioate, and 3-5 parts of tetrahydrofuran. 
 
     
     
       3. The lead-free and halogen-free solder paste according to  claim 2 , wherein the acrylic activator is prepared by the following method:
 mixing the allyl glycidyl ether, the bisphenol A diglycidyl ether and the tetrahydrofuran, adding the benzyl 1H-imidazole-1-carbodithioate, adding the acrylic acid, the acrylic anhydride and the cyclohexylamine after mixing, performing a cross-linking reaction under γ-ray radiation at a rate of 50-60 Gy/min for 30-40 min, and reacting in an oil bath of 85-90° C. for 1.5-2 h to obtain the acrylic activator. 
 
     
     
       4. The lead-free and halogen-free solder paste according to  claim 1 , wherein the composite solvent is a mixture of methyl propylene glycol, tetrahydrofurfuryl alcohol and propylene glycol monophenyl ether in a weight ratio of 1:(0.6-0.8):(0.5-0.8), respectively. 
     
     
       5. The lead-free and halogen-free solder paste according to  claim 1 , wherein the modified rosin is a mixture of a hydrogenated rosin and a disproportionated rosin in a weight ratio of 1:(2-3), respectively. 
     
     
       6. The lead-free and halogen-free solder paste according to  claim 1 , wherein the surfactant is a nonionic surfactant. 
     
     
       7. The lead-free and halogen-free solder paste according to  claim 1 , wherein the thixotropic agent is a polyurea thixotropic agent. 
     
     
       8. The lead-free and halogen-free solder paste according to  claim 1 , wherein the corrosion inhibitor is one or more selected from a group consisting of azole organic corrosion inhibitors and imidazole organic corrosion inhibitors.